I assume by default that you're applying for a PhD program in computer science; if either of these is not true, please remind me of it (repeatedly, if necessary!).
To write a letter for you, I need a month. This is because (a) I have many demands on my time, and (b) I let these letters gestate for a long time, revising draft prose in my head. The longer I get, the better the letter. More to the point, if you give me less than a month (i.e., your earliest deadline is less than a month away), I will probably decline to write a letter for you.
To write your letter, I need:
I will not upload your recommendation letters: my assistant will. You should use my name but their email address on your forms.
However: do not do this until you are told to do so! The moment you do, my assistant will get flooded with emails. This creates needless work for them, and if they miss any, some place will not get my letter for you, which will (greatly) hurt your chances.
Instead, wait for me to confirm that your letter is ready. I will notify you and my assistant at the same time (and will have shared the letter with my assistant directly).
Check with my assistant that they are ready for you to submit their email. They may be especially busy with something and may ask you to wait a little while. Please only list their email when they tell you to.
My assistant may share a spreadsheet with you asking you to list all the places you need letters sent to, your deadlines, etc. Please fill that out. That's how they make sure nothing gets missed. In turn, it helps you check on progress and catch any problems.
Most of all: Be just as respectful of my assistant's time as mine: don't make them do things in the last minute. If you rush them, they may do a sloppy job or not do it on time at all, and they (not you) will have my sympathy and support.